This invention relates to a shift actuator for moving a transfer case between high, low and neutral positions which is simplified when compared to the prior art.
Transfer cases are utilized in many medium to heavy vehicles to allow shifting between high and low ranges, and also movement into a neutral range. The transfer case typically allows rotational drive from a vehicle engine to be distributed between front and rear axles. The shift actuator allows changing the rotational drive between high and low ranges. The provision of the neutral position allows the operator to place the vehicle into neutral while still driving a power take-off. The power take-off on medium to heavy vehicles is often used to power auxiliary functions. Examples of such auxiliary functions are driving a winch, a boom for utility trucks, etc.
One challenge in providing three distinct positions is to have the shift actuator movable, and securely held at each of the three positions. Typically, cylinders are utilized to drive a shift fork between the particular positions. In one known arrangement, a valve rod moves with the shift actuator. The valve rod has two pneumatic pistons which selectively drive the rod between two positions. One piston is selectively engaged with a surface on the rod to contact and drive the rod to the third position. Typically, the known devices have required part of unique and complex configurations.
It would be desirable to provide a simplified shift actuator for vehicle transfer cases.